Thermal Quadrupole Research Articles

Thermal effusivity profile characterization from pulse photothermal data

An inversion method is proposed for depth profiling of the thermal effusivity from the surface temperature evolution after an excitation. Focus is on pulse heating. The effusivity profile is obtained through a Laplace inversion. The Stehfest method is implemented and we propose to use the number of elements in the Stehfest series N as a regularizing parameter. The optimum N value is defined by plotting a characteristic C curve with the norm of the solution derivative and the norm of the residues of the so-called apparent effusivity function. Examples of inversion results are given for linear and Gaussian effusivity profiles. For this purpose, we extended the formalism of thermal quadrupoles to the case of linearly varying effusivity. A statistical analysis is performed to assess the influence of noise on the inversion results. Recommendations on the thermogram minimum duration are derived therefrom. Experimental results obtained with a case-hardened steel sample show the potential of the present nondestructive approach.

電気化学的方法によってTiAl表面に形成された2種類の水素化物の存在領域

We have previously suggested that two kinds of hydrides (MH) are formed on the surface of titanium aluminide (TiAl) after electrochemical treatment in sulfuric acid. However, it is difficult to distinguish between the two kinds of MH from the microstructure of the specimen using normal techniques. The purpose of this study is to clarify the extent of the region in which the two kinds of MH exist across the specimen’s cross section.Depth dependence of XRD patterns were obtained by mechanically removing thin layers from the surface. It was found that the MH with the hexagonal structure (MHHEX) exists in only the outer layers, while the MH with a tetragonal structure (MHTET) exists mainly in the inner layers. Thermal desorption spectrometry and quadrupole mass spectrometry of TiAl after electrochemical treatments and Ni plating showed a complicated spectrum curve. This was caused by the decomposition of the two kinds of MH formed on TiAl as well as the MH of the Ni-plating layers at different temperatures. SEM observations of the cross section showed that the region in which the two kinds of MH exist extended 10 μm from the surface of the TiAl, with the MHHEX region extending 2 μm from the surface. MHHEX region’s hydrogen concentration was highest. The decomposition temperature of MHTET was lower than that of MHHEX. This indicates that hydrogen atoms diffuse to region of higher hydrogen concentration, which means that MHHEX is more thermally stable and has more absorption sites than MHTET.

Reconstitution of a non uniform interface thermal resistance by inverse conduction

Diffusive heat transfer problem within a non isotropic stratified structure, containing a plane defect of non uniform resistance, is solved analytically by the method of integral transforms. The idea consists in applying Fourier cosine transforms on the space variables and a Laplace transform on the time variable. The thermal quadrupole formalism allows to reduce the mathematical model to a product of matrices in the transformed space. The direct modeling, within the framework of a 2D geometry, has been followed by the construction of an inverse procedure that reconstitutes the variation of the thermal resistance from the measure of the surface temperature. But in the presence of noise, this solution becomes unstable because the problem is ill-posed. To avoid an unstable solution, a method of regularization is necessary. It consists in filtering the data to make our inverse problem well-posed The inversion can then be undertaken in an explicit way either in the transformed space, or in the real space. The established technique has been completed by a method of constrained optimization, in order to guarantee the positivity of the solution. The developed inverse codes have been validated by noised numerical simulations and by a NDT (non destructive testing) operation by stimulated infrared thermography on a bonding defect between two PVC plates.

Rare earth elements as nonabsorbable fecal markers in studies of iron absorption

The use of rare earth elements as nonabsorbable fecal markers for studies of iron absorption from sources labeled extrinsically with stable isotopes was evaluated. On 3 successive days 13 healthy fasting adults were given different stable isotopes of iron with samarium, ytterbium, or dysprosium. On day 1, three meals were given with 57Fe (1 mg per meal) plus samarium (0.33 mg per meal); on day 2, identical meals (taken with a calcium supplement to reduce iron bioavailability) were given with equivalent amounts of 58Fe-labeled iron and ytterbium; on day 3, a well-absorbed reference dose of 54Fe (3 mg) was given with 1 mg Dy. A complete fecal collection was carried out for 5-9 d and each stool was analyzed for rare earth elements by inductively coupled plasma-mass spectrometry and iron isotopes by thermal ionization quadrupole mass spectrometry. Mean recovery of rare earth elements was 101%, indicating that they are totally unabsorbed. The excretory pattern of the iron isotopes and the rare earth elements was very similar; the correlation coefficients between samarium and 57Fe, ytterbium and 58Fe, and dysprosium and 54Fe were 0.992, 0.989, and 0.988, respectively (P < 0.001). Iron absorption was calculated as the difference between isotope dose and fecal excretion. Mean (+/-SEM) iron absorption was 16.7 +/- 2.4%, 4.3 +/- 1.6%, and 40.3 +/- 3.1% on days 1-3, respectively. Predicted values estimated from the first 4 d of pooled feces, using the rare earth element recovery data to produce corrected figures for unabsorbed isotope, were in close agreement: 19.1 +/- 2.1%, 4.6 +/- 1.7%, and 40.8 +/- 3.1%, respectively (P < 0.001). With the diet of medium iron bioavailability and with the highly bioavailable reference dose it was possible to predict iron absorption accurately from only one or two stools, provided that they were sufficiently enriched with isotope and a rare earth element.

Zinc Metabolism in Non-insulin Dependent Diabetes Mellitus

Low plasma zinc concentrations and increased zinc excretion have been reported in patients with non-insulin dependent diabetes mellitus (NIDDM). This study was designed to compare zinc metabolism in ten NIDDM patients with ten healthy controls, using stable isotopes of zinc. Zinc absorption from a standard breakfast labelled extrinsically with 3 mg 67Zn was measured using a fecal monitoring technique and thermal ionization quadrupole mass spectrometry. One hour after the test meal each volunteer was given 0.5 mg 70Zn (as citrate) intravenously and blood samples taken at intervals for up to 6 days. Isotopic enrichment was measured and the data entered into a simple kinetic model to estimate the size and rate of turnover of exchangeable pools of zinc. Urinary zinc excretion was higher in the male diabetics than controls (p < 0.05), but not in females. Since the efficiency of absorption and endogenous losses of zinc were very variable between individuals, and there was only a limited amount of data, it was not possible to draw conclusion about the effect of NIDDM on zinc absorption and excretion. However, the fact that there were no differences in exchangeable zinc pool sizes suggests that zinc metabolism is not altered in NIDDM.

Differential thermal analysis and nuclear quadrupole resonance study on polymorphic 1,4-dichlorobutane

Differential thermal analysis (DTA), and the 35Cl nuclear quadrupole resonance (NQR) frequency (v Q ) and line width (Δv Q ) were measured as a function of the temperature in solid 1,4-Dichlorobutane (DCB). Two crystalline modifications forms I and II, stables above and below T c = 210 K respectively were found according to the thermal history of the sample. A comparative analysis of the NQR frequency in both phases suggests that the crystal structure in form II is closer-packed than in form I. The NQR line width shows the existence of a thermal activated process with an activation energy E a ≃ 20 kJ mol−1, probably related with reorientations of the CH2Cl end groups. Some orientational disorder is expected in the low temperature modification since the line width is twice as much as that in the high temperature phase.

Simultaneous TA and MS analysis of alternating styrene-maleic anhydride and styrene-maleimide copolymers

The thermal behaviours of alternating styrene-maleic anhydride copolymer (St/MAn), styrene-methyl maleimide copolymer (St/MMI) and copolymers with different contents of MMI were studied by means of a simultaneous thermal analyser and quadrupole mass spectrometer system (STA/QMS). In addition, special measurements were carried out by a pyrolysis-gas chromatography-mass spectrometer (Py-GC-MS) and a differential scanning calorimeter (DSC). The glass transition of the copolymers in influenced by the degree of imidization. The decomposition behaviour of pure styrene-maleic anhydride copolymer differs from that of styrene-methyl maleimide copolymer. The favoured process of degradation of maleic anhydride-rich structures is reaction in the chains, and that of methyl maleimide-rich structures is the random chain break.

Thermal multipoles for a jet in ambient spathermal multipoles for a jet in ambient space

A general solution of the thermal problem for a non-self-similar axisymmetric jet is determined on the basis of the multiple approach developed for problems of non-self-similar jets in ambient space [1, 2], and several problems of convective heat-transfer in simply- or doubly-connected domains are solved. The advantage of expanding the solution of the convective heat conduction equation in eigenfunctions of the problem is demonstrated. As an illustration, the solutions for a thermal dipole and quadrupole and for a jet flow in a heated tube are presented. The corresponding solutions are also obtained for a turbulent jet in ambient space. The most favorable heat-exchange regime for a jet in a heated tube is predicted on the basis of the particular behavior of the eigenfunctions of the thermal problem.

Total evaporation measurements: experience with multi-collector instruments and a thermal ionization quadrupole mass spectrometer

Results and experience are presented for a method of “fractionation free” measurements in thermal ionization mass spectrometery. The method can be used not only on multi-collector mass spectrometers, where the isotopes of interest can be measured simultaneously, but also on a thermal ionization quadrupole mass spectrometer using a special scanning and heating sequence. The total evaporation method strongly decreases the errors due to uncorrected fractionation when the amount of sample loaded on the filament varies widely. Resin beads containing only 1 ng of U and/or Pu can also be analyzed. The performance is demonstrated on uranium and plutonium samples.

Width of the plasmon resonance in metal clusters.

The width of the plasmon resonance in the clusters ${\mathrm{Na}}_{9}^{+}$, ${\mathrm{Na}}_{21}^{+}$, and ${\mathrm{Na}}_{41}^{+}$ is investigated in the framework of the structure-averaged jellium model and compared with recent experimental data. The two leading mechanisms for the line broadening are fragmentation of the resonance into nearby 1ph states and splitting through thermal quadrupole fluctuations. The fragmentation becomes activated mainly through octupole fluctuations and it gives the dominating contribution to the width.

Determination of heavy metals in TiO2 with isotope dilution mass spectrometry

An isotope dilution mass spectrometric (IDMS) method has been developed for the determination of trace impurities (Fe, Cu, Cr, Ni, Cd, Pb, Tl, and U) in TiO2; this is of special interest for the quality control of this pigment substance. The measurement of the isotope ratios was carried out using a compact thermal ionization quadrupole mass spectrometer by producing positive thermal ions. For the dissolution of the sample, microwave digestion with HF was applied. Different separation techniques (ion exchange chromatography, extraction, electrolytic deposition) were used for the trace/matrix separation and the element specific isolation of the different trace elements to be determined. The detection limits obtained were (in ng/g): Fe=90, Cu=11, Ni=8, Cd=7, Pb=26, Tl=0.6, U=0.2. Because IDMS usually results in accurate analytical results, this method can best be used for calibration of other analytical methods, or for the certification of corresponding standard reference materials.

Thermal hystersis and quadrupole interactions in ferroelectric transitions.

Abstract It is shown that a selfconsistent calculation of the maximum amount of thermal hystersis accompanying discountinous ferroelectric transtion can be made if one takes into account the quadrupolar contribution to the effective ferroelectric field. Comparison of calculated and observed thermal hystersis in sereral ferroelectrics belonging to different families shows fair agreement.

Isotope dilution mass spectrometry of microelectronically relevant heavy metal traces in high-purity cobalt

Because cobalt and its silicides are increasingly used in microelectronic devices, an isotope dilution mass spectrometric (IDMS) method has been developed for trace analysis of relevant heavy metals (U, Th, Fe, Zn, Tl, and Cd) in high-purity cobalt. The measurements of the isotope ratios were carried out with a small thermal ionization quadrupole mass spectrometer by producing positive thermal ions in a single- or double-filament ion source. For the trace/matrix separation and the isolation of the different heavy metals, anion-exchange chromatography and an extraction method for iron were applied. The detection limits obtained were (in ng/g): U=0.007, Th=0.017, Tl=0.06, Cd=1, Zn=8, and Fe=11, which demonstrates that the particularly critical radioactive impurities uranium and thorium could be analysed down to the low pg/g range. Three cobalt samples of different purity were analysed with concentrations ranging from about 0.1 ng/g for U and Th in an ultra high-purity material produced for microelectronic purposes, up to about 70 μg/g for Cd in a cobalt sample with declared purity of 99.8%. Because IDMS usually results in accurate analytical results, it can be used in the future for calibration of other methods like glow discharge mass spectrometry, as could be shown by analysing one cobalt sample by both methods. IDMS can also be applied for the production of urgently needed certified standard reference materials in this important field of high technology.

Trace analyses of U, Th and other heavy metals in high purity aluminium with isotope dilution mass spectrometry

A method for the determination of very low concentrations of U, Th, Fe, Zn, Tl, Cd, Cu and Ag in high purity aluminium with isotope dilution mass spectrometry (IDMS) is developed using a compact and cost-efficient thermal ionization quadrupole mass spectrometer. The detection limits obtained are (in ng/g):U=0.018, Th=0.06, Fe=82, Zn=86, Tl=0.2, Cd=4, Cu=1, Ag=2.6. By this method it is possible to determine the α-emitters U and Th in aluminium down to the sub-ng/g level with good precision of 0.4–10% and 0.5–5%, respectively. The results should also be accurate because IDMS is a reliable analytical method. The dissolution of aluminium is carried out by aqua regia followed by the trace/matrix separation and the isolation of the trace elements by anion exchange chromatography (U, Th, Zn, Tl, Cd), electrodeposition (Cu, Ag) and extraction (Fe). Different aluminium samples are analysed by IDMS and the results are compared with those of other methods.

Free convection near a thermal quadrupole

A conically self-similar solution of the Boussinesq equations is reported. Thermogravitational convection near a quadrupolar point singularity of a temperature field is studied. At a Prandtl number of zero the solution loses its existence when the Grashof number achieves some critical value. If the Prandtl number differs from zero, then the solution exists at any Grashof number but, when the Prandtl number tends to zero, the passage to the limit can become nontrivial. At subcritical Grashof numbers, a strong upward jet is developed. A number of problems are studied in which the flow region is bounded by a conical surface. These problems may serve as simple models of convection near a volcano, a glacier, and an iceberg.

Thermo field boson realizations for operators of the finite temperature random phase approximation

A Dyson boson realization for two-quasiparticle operators at finite temperature is derived by using the thermo field dynamic formalism. The operators of the finite temperature random phase approximation (FT-RPA) are constructed from the zero temperature two-quasiparticle operators. The conditions are found under which these thermal RPA quadrupole operators close the SU (6) algebra. The fulfillment of the SU (6) enforcing conditions at finite temperature is discussed.

Self-similar convection near a thermal quadrupole

The self-similar solution is constructed for the Boussinesq equations describing free convection near a differentially heated local section on a horizontal plane.

Fluctuations in the shape transitions of hot nuclei.

The effect of quantal and thermal quadrupole shape fluctuations in the giant dipole response function of hot nuclei at high spin is studied within the Landau theory of phase transitions. The effects are found to be important in the relation of the nuclear shape to the experimental findings, and in the identification of shape phase transitions.

Iron isotope ratio measurements with the thermal ionization technique using a compact quadrupole mass spectrometer

A new technique, using boric acid in addition to silica gel, was developed to determine iron isotope ratios with thermal ionization mass spectrometry. The Fe + thermal ion current depends on the filament temperature with a maximum intensity at 1370°C. The ion current could be increased by a factor of 3–4 by small amounts of organic substances in the sample, e.g. from decomposition products of ion exchange resins or from plasticizers contained in PE flasks. The ion current is also dependent on the amount of other heavy metals in the sample. For example, the Fe + current was decreased by a factor of more than 30 by adding 8 μg of chromium. The 54Fe/ 56Fe isotope ratio in a sample of natural isotopic composition could be determined with a relative standard deviation of 0.3% using a compact thermal quadrupole and a large magnetic sector field mass spectrometer. This gave better reproducibility than that previously obtained with other mass spectrometric instrumentation. To show the applicability of the new technique in connection with the quadrupole mass spectrometer, isotope dilution mass spectrometry was carried out to determine iron traces in biological standard reference materials and in different water samples. The applicability for bioavailability studies was also demonstrated.

Chromspurenbestimmungen in anorganischen, organischen und w��rigen Proben mit der massenspektrometrischen Isotopenverd�nnungsanalyse

It is shown that chromium traces in different inorganic, organic and aqueous samples can be determined over a wide concentration range with isotope dilution mass spectrometry. Electrolytic or chromatographic isolation steps are added to a system of sample preparation units for oligo-element determinations to analyse chromium besides other heavy metals. The isotope ratio52Cr/53Cr is measured in a thermal quadrupole mass spectrometer using a single-filament ion source with additions of silica gel and boric acid. In water samples, which contain humic substances, chromium concentrations of a few ng/g and less can be determined with relative standard deviations of about 1% and better. A differentiation is possible into the total chromium content and into chromium species which carry out isotope exchange reactions and those which are inert for an isotope exchange reaction. The chromium concentrations of four standard reference materials (two plants BCR 60 and 61, one tissue BCR 278, one sewage sludge BCR 144), which are not certified for chromium, are determined to be 29.4 Μg/g, 534 Μg/g, 0.78 Μg/g, and 466.1 Μg/g, respectively. In three different sediments total chromium concentrations between 100 Μg/g and 180 Μg/g are analysed with relative standard deviations of 0.6%–1.2%. Using aqua regia instead of nitric acid and hydrofluoric acid for the decomposition of sediments, only 60%–90% of the total chromium content is determined. However, the analysed chromium proportion dissolved in aqua regia is slightly higher when using isotope dilution mass spectrometry compared with other analytical methods. The detection limit is 0.3 pg chromium per g for water samples, 1.8 ng/g for organic substances, and 6 ng/g for materials with high inorganic proportions as for sediments, sewage sludges and soils.